In 3GPP (3rd Generation Partnership Project) specification, there are two basic subframe types. One type is unicast subframe and the other type is MBSFN (Multimedia Broadcast multicast service Single Frequency Network) subframe.
Unicast subframe is used for data and control channel transmission to specific UE so that one-to-one communication may be performed between eNB and UE.
On the contrary, the MBSFN subframe is used for broadcasting signals which includes data and a control channel to targeted multiple receivers (e.g., UE).
In the MBSFN subframe, a Release-8 UE does not know about the MBSFN subframe structure except the first control channel part (length is indicated by PCFICH (Physical control format indicator channel)). Thus, the method for identifying a MBSFN subframe at the Release-8 UE is required.
Meanwhile, the MBMS feature is introduced into Release-9 specification, and thus a Release-9 UE needs to decode the MBSFN subframe. However, since the feature of MBMS is just one of the targeting subframe types, this MBSFN subframe is not defined as single subframe type. For example, as with dual cell/dual stream beamforming, a Release-9 UE may operate in a different operation mode with legacy UE while achieving better throughput via MBSFN configuration.
In addition, LTE-A system (Release-10 or later system) may employ various new features considering higher order MIMO, CoMP (Coordinated Multi-Point), Relay, and so on. Thus, additional new subframe types are required.
However, a method for indicating MBSFN subframe and MBSFN subframe type to release-8 UE, release-9 UE, and LTE-A UE are not studied yet.